unable to correct filters for proper notch freq.

[LearningLots]

Hello All,
Tonight I calibrated and set up my nano vna as directed in Dl2MAN text and video.
My tr usdx was purchased assembled from uellyqh the authorized ebay seller. The only bands I care about are 20/40/80.
20 outputs 4.3 W @ 63% eff. @12v
40 outputs 2.2 W @ 54% eff. @12v
80 outputs 5.1 W @ 69% eff. @12v
The VNA places the 20 notch at 29mhz (should be 28 I believe). The 40 notch at 13.690 and the 80 notch at
7.130.
I tried adjusting (spreading) the 40 meter coil to try and move the notch up but could not move it much at all. I then removed one turn and the notch moved up too much. I then rewound it back to 10 turns and my low notch returned. Maybe the caps are wrong??? I'll change them if I can get the right caps.
80 meters is acceptable but the eff is lousy, and 20 meters needs notch adjustment and better eff.
Any ideas?
I had hoped an assembled tr usdx would have required little adjustment but I was wrong.

[s57l]

It is impossible to spread the turns more, but easy to squeeze them. Remove one turn and adjust by squeezing. Does not look that neet as if they are spread evenly, but it does the job.
You should probably not touch the caps...
I was in a group buy, so different source, but i removed at least one turn on almost every coil...
73 gl
Janko s57l

[N6YWU]

If 10 turns are too many, try 9 turns again, but this time leave the leads long enough to allow a lot more of scrunching of the turns to move the notch back down.

According to figure D on page 4 of this Micrometals document:

http://www.iec-international.com/microm ... ue%20H.pdf

scrunching the turns to use only 120 degrees (one third) of a toroid can increase the inductance by over 50%. That range of inductance variation should allow you to move the notch enough to get to the right frequency.

So make sure the leads are long enough that you can move all the turns to the opposite third of the toroid, and you will have a wider range of notch frequency adjustment. After adjusting the turn spacing, if there's lots spare wire between the PCB and the toroid, you can try shortening the wire slop bit-by-bit by re-soldering, and checking the frequency as you go.

73, Ron, N6YWU

[LearningLots]

Thank you both very much! I see my mistake, I cut off the turn I had removed. Tonight I will again remove one turn but leave it attached so that I can better adjust the remaining coils.
I gotta stop making things look pretty and concentrate on getting the mechanical and electrical result that I am aiming for.